Abstract
The purpose of this paper is to reduce the theory of mechanics to a minimum set of principles. Assuming the existence of conservation laws, the author shows that the form of these laws is completely determined by the fundamental symmetries of the galilean reference frame, without using pre-established kinematics: the expressions of these laws correspond to Einsteinian mechanics, including those of Leibnitzian or Newtonian mechanics as a limiting case. In this way, the existence of an upper limit of the velocity of energy propagation and the mass-energy equivalence are deduced from the fundamental symmetries.